Release of [3h]gamma‐aminobutyric Acid From Glial Cells in Rat Dorsal Root Ganglia.

Desheathed rat dorsal root ganglia were incubated in a medium containing amino‐oxyacetic acid and [3H]GABA. Under these conditions, [3H]GABA is taken up exclusively by the satellite glial cells in the ganglia. Efflux of [3H]GABA from the tissue was measured after passing the ganglia through a series of wash solutions. The spontaneous efflux of radioactivity, mostly [3H]GABA, was more rapid in the absence of amino‐oxyacetic acid in the incubation and wash media. Raising the potassium concentration in the wash media caused an increase in the efflux of [3H]GABA. This increase was sigmoidally related to the potassium concentration in the wash media, reaching a maximum at 64 mm‐K+. The releasing effect of K+ was inhibited by removing calcium from the media. Reducing the calcium and raising the magnesium concentration in the wash solutions inhibited the increased efflux of [3H]GABA due to 64 mm‐K+ by 48 per cent, while 5 mM‐La3+ and diphenylhydantoin (0·005 and 0·5 mm) had no effect on this increase. Only a small increase in the efflux of [14C]glutamate was produced by 64 mm‐K+ and it had no effect upon the effluxes of [3H]glycine, [3H]alanine or [3H]leucine. The efflux of lactate dehydrogenase was similarly unaffected by 64 mM‐K+. The results suggest that glial cells in spinal ganglia can respond to depolarizing concentrations of potassium by releasing GABA in a calcium‐dependent process.